Multi-arm disk drive system having interleaved read/write operations and method of controlling same

ABSTRACT

A hard disk drive system that includes one or more rotating data storage platters, a drive controller and multiple actuator assemblies and corresponding respective read/write heads. The actuator assemblies are separately moveable for performing separate data seeks. The controller is configured to interleave the seek and read/write operations of the multiple actuator assemblies and read/write heads with one another.

RELATED APPLICATION DATA

This application is a continuation application of U.S. Nonprovisionalpatent application Ser. No. 11/278,283 filed on Mar. 31, 2006 and titled“Multi-Arm Disk Drive System Having Interleaved Read/Write Operationsand Method of Controlling Same,” which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to the field of non-volatiledata storage. In particular, the present invention is directed to amulti-arm disk drive system having interleaved read/write operations andmethod of controlling same.

BACKGROUND OF THE INVENTION

Hard disk drives are used in many applications where relatively fast,economical, non-volatile mass storage is desired. For example, hard diskdrives are commonly used in computer servers, mainframe computers,personal computers, laptop computers, digital video recorders, music andmultimedia devices, personal digital assistants, digital cameras andcellular telephones, among other things. Hard disk technology hasevolved significantly since the first commercial hard disk drive becameavailable in 1956.

Present hard disk drives typically include a plurality of platters thatspin at a constant angular velocity about a common rotational axis, orspindle. Common form factors, or platter diameters, of presentgeneration hard disk drives are 3.5 in., 2.5 in., 1.8 in., 1 in. and0.85 in. That said, other diameter platters are available. The plattersare typically made of a non-metallic material, e.g., glass or aluminum,coated on both major surfaces with a magnetic recording material,typically iron oxide, that form the data storage surfaces of the drive.Present hard disk drives typically have a single armature that movesmultiple read/write heads, one for each data storage surface, in unisonwith one another.

Several more recent designs utilize multiple read/write heads per datastorage surface and move these multiple heads with correspondingrespective independent armatures. In some of these designs, the multipleheads are used for redundancy or for increasing the speed of a givendata transfer (read or write) operation by using some or all of theread/write heads simultaneously for that data transfer. In others ofthese designs, the multiple heads per data storage surface arecontrolled so that the read/write head closest to the location of thedata at any given time is used for the data transfer. The one or moreremaining read/write heads for that surface do not participate in thatdata transfer and await subsequent data transfer requests that call theminto action. While these recent simultaneous read/simultaneous write andclosest-to-the-data designs increase the speed of the respective harddisk drives, improvement in the average seek time, i.e., the averagetime it takes for the read/write head(s) to be moved to a desired datatransfer location over a plurality of read/write requests, is highlydesirable.

SUMMARY OF THE INVENTION

In one aspect, the present invention is directed to a disk drive systemresponsive to a plurality of data transfer requests received in atemporally sequential order and requiring a plurality of correspondingrespective seeks and a plurality of corresponding respective datatransfers. The disk drive system includes a housing; at least oneplatter rotatably mounted within the housing, the at least one platterhaving a first data storage surface containing a plurality of surficialdata storage locations; a first read/write head movably mounted withinthe housing and configured to read and write data to ones of theplurality of surficial data storage locations; a first actuator assemblysupporting the first read/write head and configured to move the firstread/write head so that the first read/write head is able to access theplurality of surficial data storage locations; at least a secondread/write head movably mounted within the housing and configured toread and write data to ones of the plurality of surficial data storagelocations; a second actuator assembly supporting the second read/writehead and configured to move the second read/write head independently ofthe first read/write head and so that the second read/write head is ableto access the plurality of surficial data storage locations; and acontroller operatively connected to the first actuator assembly and thesecond actuator assembly, the controller responsive to the plurality ofdata transfer requests by interleaving the plurality of correspondingrespective seeks between the first actuator assembly and the secondactuator assembly, the controller operatively configured to stall onesof the plurality of corresponding respective data transfers as neededmaintain the plurality of corresponding respective data transfers in anorder consistent with the temporally sequential order of plurality ofdata transfer requests.

In another aspect, the present invention is directed to a method ofcontrolling a disk drive that includes at least one platter having atleast one storage surface, the disk drive further including at least tworead/write heads in working relationship with the at least one storagesurface. The method includes receiving, in a temporally sequentialorder, a plurality of data transfer requests that require a plurality ofcorresponding respective seeks and a plurality of correspondingrespective data transfers; moving the at least two read/write heads soas to interleave the plurality of corresponding respective seeks withone another; activating the at least two read/write heads so as toperform the plurality of corresponding respective data transfersrelative to the at least one storage surface; and selectively stallingeach of the plurality of corresponding respective data transfers asneeded to maintain the plurality of corresponding respective datatransfers in an order consistent with the temporally sequential order ofthe plurality of data transfer requests.

In yet another aspect, the present invention is directed to a disk drivesystem responsive to a plurality of temporally sequential data transferrequests requiring a plurality of corresponding respective seeks and aplurality of corresponding respective data transfers. The disk drivesystem includes a housing; at least one platter rotatably mounted withinthe housing, the at least one platter having a first data storagesurface containing a plurality of surficial data storage locations; afirst read/write head movably mounted within the housing and configuredto read and write data to ones of the plurality of surficial datastorage locations; a first actuator assembly supporting the firstread/write head and configured to move the first read/write head so thatthe first read/write head is able to access the plurality of surficialdata storage locations; at least a second read/write head movablymounted within the housing and configured to read and write data to oneof the plurality of surficial data storage locations; a second actuatorassembly supporting the second read/write head and configured to movethe second read/write head independently of the first read/write headand so that the second read/write head is able to access the pluralityof surficial data storage locations; and a controller operativelyconnected to the first actuator assembly and the second actuatorassembly, the controller responsive to the plurality of temporallysequential data transfer requests by performing the plurality ofcorresponding respective seeks in the temporally sequential order byalternating the plurality of corresponding respective seeks between thefirst actuator assembly and second actuator assembly, the controlleroperatively configured to stall ones of the plurality of correspondingrespective data transfers as needed to maintain the plurality ofcorresponding respective data transfers in an order consistent with thetemporally sequential order of the plurality of data transfer requests.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show a formof the invention that is presently preferred. However, it should beunderstood that the present invention is not limited to the precisearrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 is a plan view of a disk drive system of the present inventionwith the cover removed;

FIG. 2 is an enlarged cross-sectional view of the disk drive system ofFIG. 1;

FIG. 3 is a timing diagram illustrating the seek and data transferoperations of the disk drive system of FIG. 1; and

FIG. 4 is flow diagram showing an interleaving scheme of controlling theseek and data transfer operations of the disk drive system of FIG. 1.

DETAILED DESCRIPTION

Referring now to the drawings, FIGS. 1 and 2 illustrate a multi-armaturehard disk drive (HDD) system 100 of the present invention that, asdiscussed below in much more detail, includes various features thatreduce the average seek time of the system relative to conventionalsingle and multi-arm HDD systems. HDD system 100 may include a housing102 that contains one or more platters 104, such as the four platters104A-D particularly shown in FIG. 2, that are rotatable about a commonspindle 108 relative to the housing. Each platter 104A-D may have firstand second data storage surfaces 112A-B, which may be provided with itsdata storage capacity in any suitable manner. For example, each datastorage surface 112A-B may have a magnetic storage surface comprisingiron oxide or other magnetic material. The details of manufacturingplatters 104A-D suitable for use with the present invention are wellknown in the art and, therefore, need not be described in any detailherein for those skilled in the art to understand the broad scope of thepresent invention.

HDD system 100 may further include a plurality of actuator assemblies,e.g., the two armature assemblies 116A-B shown, that each support andmove a set of read/write heads 120A-B independently of one another. Thenumber of read/write heads 120A-B on each assembly 116A-B will typicallycorrespond to the number of data storage surfaces 112A-B. In thisconnection, it is noted that any given read or write request may involvethe use of one or more of read/write heads 120A or read/write heads 120Bin satisfying that request. Each armature assembly 116A-B may include anarmature 124A-B and an actuator 128A-B operatively configured to movethe respective armature during a data location seek. Each actuator128A-B may include, e.g., a linear motor, voice coil, etc. (not shown)for moving the respective armature 124A-B. Those skilled in the art willreadily appreciate that while pivoting type actuator assemblies 116A-Bare shown, other types of actuator assemblies, e.g., linear movementtype actuator assemblies, may also be used with a disk drive system ofthe present invention. A variety of multi-head arrangements and actuatorassembly types suitable for use with the present invention are shown inU.S. Pat. No. 6,883,062 to Susnjar, which is incorporated herein byreference for its disclosure of the various arrangements and actuatorassembly types.

The operation of each armature assembly 116A-B and each read/write head120A-B may be controlled by a suitable controller 132, which may alsoprovide an interface between HDD system 100 and whatever device(s) (notshown), e.g., one or more computer servers, mainframe computers,personal computers, laptop computers, digital video recorders, music andmultimedia devices, personal digital assistants, digital cameras,cellular telephones, etc., to which the HDD system is connected. Asthose skilled in the art will appreciate, controller 132 may beimplemented in any suitable hardware, software or combination ofhardware and software. The functionality of controller 132 is discussedin much more detail below.

In general, HDD system 100 receives from such device(s) one or morecontinual flows of data transfer requests, i.e., requests for eitherreading specific data from data storage surfaces 112A-B of platters104A-D or writing specific data to the data storage surfaces.Accompanying the write requests, controller 132 will typically alsoreceive the data to be written to data storage surfaces 112A-B.Consequently, controller 132 may include the functionality required tocoordinate the writing of data to data storage surfaces 112A-B so thatit may be read in response to an appropriate read request. Controller132 will typically also output the data corresponding to the readrequests. Therefore, controller 132 may also be provided withfunctionality required to coordinate the data read from the data storagesurfaces 112A-B with the corresponding respective read requests. It isnoted that while controller 132 is shown located inside housing 102, inother embodiments the controller may be located outside the housing.

As mentioned above, an important feature of HDD system 100 is itsability to reduce the average seek time needed to respond to a set ofdata transfer requests. This may be accomplished by interleaving withone another the data transfer operations, e.g., seek-and-write orseek-and-read operations, performed by HDD system 100 in response to thevarious incoming data transfer requests. This interleaving functionalitymay be provided by controller 132. For example, one interleaving schemesuitable for use with HDD system 100 of FIGS. 1 and 2 is illustrated bythe timing diagram 200 of FIG. 3. Referring to FIG. 3, and also to FIGS.1 and 2, timing diagram 200 of FIG. 3 illustrates the data transferoperation sets 204A-D of armature assembly 116A and read/write head 120Aand the data transfer operation sets 208A-D of armature assembly 116Band read/write head 120B corresponding to an exemplary set of eighttemporally sequential data transfer requests 212A-H. Each data operationset includes a seek 216 and a data transfer 220A-H, i.e., either a reador write depending upon the nature of the corresponding data transferrequest 212A-H.

The interleaving scheme illustrated by timing diagram 200 is based onthe concept of performing the data transfers 220A-H of the multiple datatransfer operation sets 204A-D, 208A-D in the same temporally sequentialorder as the receipt of data transfer requests 212A-H. This isaccomplished by adding a stall cycle 224 to each data transfer operationset 204A-D, 208A-D in which the seek 216 of that set is finished beforethe data transfer 220A-H of the immediately prior data transfer request212A-H is completed. The length of each stall cycle 224 may be thelength of time needed for the immediately preceding data transfer 220A-Hto end, plus any time needed for controller 132 or other circuitry to beready to handle another data transfer. Of course, if a seek 216 andcorresponding data transfer 220A-H are completed for a particular datatransfer request 212A-B before the seek is completed for the immediatelyfollowing request, then a stall cycle is not necessary.

Maintaining the temporal sequential order in the data transfers 220A-H,as is done in the interleaving scheme illustrated in FIG. 3, generallysimplifies the functionality of controller 132 in that the controller isnot responsible for tracking and correlating unordered data transfers,particularly reads, with the temporally sequentially ordered datatransfer requests 212A-H. That said, in alternative embodiments of thepresent invention, the interleaving of data request operation need notresult in such ordered data transfers. For example, in one alternativeembodiment (not shown) as soon as a data transfer is complete, the nextseek to perform may take place. If the corresponding controller wereconfigured to handle only one data transfer at a time, a stall cyclecould be added to prevent a data bus conflict. On the other hand, if thecontroller were configured to simultaneously handle a number of datatransfers equal to the number of read/write heads, then such stallcycles would not be needed. In either of these alternative interleavingschemes, the controller or other circuitry would need to includefunctionality for correlating the data read transfers, particularly thereads, with the corresponding respective data read requests. This wouldadd to the complexity of the controller or other circuitry.

Referring to FIG. 4, and also to FIGS. 1-3, FIG. 4 illustrates a flowdiagram 300 for performing the interleaving scheme illustrated in timingdiagram 200 of FIG. 3 within HDD system 100 of FIGS. 1 and 2. At step305, controller 132 receives a data transfer request. At step 310,controller 132 determines whether or not armature assembly 116A and/orcorresponding read/write head(s) 120A are busy handling a prior datatransfer request. If not, at step 315 controller 132 activates armatureassembly 116A so as to position the appropriate read/write head 120A atthe proper location for performing the requested data transfer to orfrom the corresponding data storage surface 112A-B. Step 315 may bereferred to as a seek step. After seek step 315, at step 320 controller132 determines whether or not the other armature assembly 116B and/orcorresponding read/write head(s) 120B are busy with a prior request. Ifso, the interleaving scheme enters a stall loop 325 that continues toexecute until the other armature assembly 116B and/or correspondingread/write head(s) 120B are done with the prior request. It is notedthat the effect of stall loop 325 is not illustrated in FIG. 3. However,referring to FIG. 3, its effect can be visualized by extending seek 216associated with data transfer request 212D beyond the data transfer 220Eassociated with request 212E. In this case, stall loop 325 would notpermit the data transfer 220E of data transfer request 212E to occuruntil after the data transfer 220D of request 212D by inserting a stallcycle 224 between the seek 216 and the data transfer 220E of request212E.

If, on the other hand, the other armature assembly 116B and/orread/write head (s) 120B are not busy with a prior data transfer requestat step 320, the interleaving scheme may proceed to step 330 at whichcontroller 132 causes the data transfer from or to the correspondingrespective data storage surface(s) 112A-B to occur for the currentrequest. Once the data transfer has been completed, the interleavingtechnique may cycle back to step 305 at which point another datatransfer request is received by controller 132.

If at step 310 controller 132 had determined that armature assembly 116Aand/or read/write head(s) 120A were busy with a prior data transferrequest, the controller may determine at step 335 whether or notarmature assembly 116B and/or read/write head(s) 120B are busy with aprior request. If so, the interleaving scheme may enter a wait loop 340that continues until one or both armature assemblies 116A-B andcorresponding respective read/write heads 120A-B are no longer busy witha prior request. If at step 335 controller 132 determines that armatureassembly 116B and read/write head(s) 120B were not busy (and armatureassembly 116A and read/write head(s) 120A were busy at step 310), atstep 345 controller 132 activates armature assembly 116B so as toposition read/write head(s) 120B at the proper location for performingthe requested data transfer to or from the corresponding data storagesurface(s) 112A-B. Step 345 may be referred to as a seek step. Afterseek step 345, at step 350 controller 132 determines whether or not theother armature assembly 116A and/or corresponding read/write head(s)120A are busy with a prior request. If so, the interleaving schemeenters a stall loop 355 that continues to execute until the otherarmature assembly 116A and/or corresponding read/write head(s) 120A aredone with the prior request. The effect of stall loop 355 is illustratedtwice in FIG. 3, once in connection with data transfer request 212B andonce in connection with data transfer request 212F.

If, on the other hand, the other armature assembly 116A and/orread/write head(s) 120A are not busy with a prior data transfer requestat step 350, the interleaving scheme may proceed to step 360 at whichpoint controller 132 causes the data transfer from or to thecorresponding respective data storage surface(s) 112A-B to occur for thecurrent request. Once the data transfer has been completed, theinterleaving technique may cycle back to step 305 at which point anotherdata transfer request is received by controller 132.

Those skilled in the art will readily appreciate that the interleavingscheme illustrated by flow diagram 300 of FIG. 4 is merely exemplary andthat a variety of alternative interleaving schemes are possible and maybe readily implemented with an understanding of the present disclosure.

Although the invention has been described and illustrated with respectto an exemplary embodiment thereof, it should be understood by thoseskilled in the art that the foregoing and various other changes,omissions and additions may be made therein and thereto, without partingfrom the spirit and scope of the present invention.

1. A disk drive system responsive to a plurality of data transferrequests received in a temporally sequential order and requiring aplurality of corresponding respective seeks and a plurality ofcorresponding respective data transfers, the disk drive systemcomprising: a housing; at least one platter rotatably mounted withinsaid housing, said at least one platter having a first data storagesurface containing a plurality of surficial data storage locations; afirst read/write head movably mounted within said housing and configuredto read and write data to ones of said plurality of surficial datastorage locations; a first actuator assembly supporting said firstread/write head and configured to move said first read/write head sothat said first read/write head is able to access said plurality ofsurficial data storage locations; at least a second read/write headmovably mounted within said housing and configured to read and writedata to ones of said plurality of surficial data storage locations; asecond actuator assembly supporting said second read/write head andconfigured to move said second read/write head independently of saidfirst read/write head and so that said second read/write head is able toaccess said plurality of surficial data storage locations; and acontroller operatively connected to said first actuator assembly andsaid second actuator assembly, said controller responsive to theplurality of data transfer requests by interleaving the plurality ofcorresponding respective seeks between said first actuator assembly andsaid second actuator assembly, said controller operatively configured tostall ones of the plurality of corresponding respective data transfersas needed to maintain the plurality of corresponding respective datatransfers in an order consistent with the temporally sequential order ofplurality of data transfer requests.
 2. A disk drive system according toclaim 1, wherein said controller configured to control said first andsecond actuator assemblies so as to perform said plurality ofcorresponding respective seeks in the temporally sequential order byalternating the plurality of corresponding respective seeks between saidfirst and second actuator assemblies.
 3. A disk drive system accordingto claim 1, wherein said controller configured to control said first andsecond read/write heads so as to perform said plurality of correspondingrespective data transfers in the temporally sequential order bysequentially alternating the plurality of corresponding respective datatransfers between said first and second read/write heads.
 4. A diskdrive system according to claim 3, wherein said controller is configuredto control said first and second actuator assemblies so as to performsaid plurality of corresponding respective seeks in the temporallysequential order by sequentially alternating the plurality ofcorresponding respective seeks between said first and second actuatorassemblies.
 5. A disk drive system according to claim 1, wherein said atleast one platter comprises first and second data storage surfaces andsaid plurality of surficial data storage locations are contained on saidfirst and second data storage surfaces, the disk drive system furthercomprising a first pair of read/write heads supported by said firstactuator assembly and a second pair of read/write heads supported bysaid second actuator assembly, each of said first and second pairs ofread/write heads containing a read/write head operable with said firstdata storage surface and a read/write head operable with said seconddata storage surface.
 6. A disk drive system according to claim 1,further comprising a plurality of platters each including a first andsecond data storage surface, said plurality of surficial data storagelocations being contained on said first and second data storage surfacesof said plurality of platters, the disk drive system further comprisinga first set of read/write heads supported by said first actuatorassembly and a second set of read/write heads supported by said secondactuator assembly, each of said first and second sets of read/writeheads having a read/write head operable with a corresponding respectiveone of said first and second storage surfaces of said plurality ofplatters.
 7. A disk drive system according to claim 1, wherein each ofsaid first and second actuator assemblies comprises a pivoting armature.8. A method of controlling a disk drive that includes at least oneplatter having at least one storage surface, the disk drive furtherincluding at least two read/write heads in working relationship with theat least one storage surface, the method comprising: receiving, in atemporally sequential order, a plurality of data transfer requests thatrequire a plurality of corresponding respective seeks and a plurality ofcorresponding respective data transfers; moving the at least tworead/write heads so as to interleave said plurality of correspondingrespective seeks with one another; activating the at least tworead/write heads so as to perform said plurality of correspondingrespective data transfers relative to the at least one storage surface;and selectively stalling each of the plurality of correspondingrespective data transfers as needed to maintain the plurality ofcorresponding respective data transfers in an order consistent with thetemporally sequential order of the plurality of data transfer requests.9. A method according to claim 8, wherein said activating of the atleast two read/write heads includes activating the at least tworead/write heads so as to interleave said plurality of correspondingrespective data transfers.
 10. A method according to claim 8, whereinsaid moving of the at least two read/write heads includes moving the atleast two read/write heads so that said plurality of correspondingrespective seeks are initiated in the temporally sequential order.
 11. Amethod according to claim 10, wherein said moving of the at least tworead/write heads includes moving the at least two read/write heads in analternating manner.
 12. A method according to claim 11, wherein saidactivating of the at least two read/write heads includes activating theat least two read/write heads so as to perform said plurality ofcorresponding respective data transfers in the temporally sequentialorder.
 13. A method according to claim 12, wherein said activating ofthe at least two read/write heads includes activating the at least tworead/write heads in an alternating manner.
 14. A disk drive systemresponsive to a plurality of temporally sequential data transferrequests requiring a plurality of corresponding respective seeks and aplurality of corresponding respective data transfers, the disk drivesystem comprising: a housing; at least one platter rotatably mountedwithin said housing, said at least one platter having a first datastorage surface containing a plurality of surficial data storagelocations; a first read/write head movably mounted within said housingand configured to read and write data to ones of said plurality ofsurficial data storage locations; a first actuator assembly supportingsaid first read/write head and configured to move said first read/writehead so that said first read/write head is able to access said pluralityof surficial data storage locations; at least a second read/write headmovably mounted within said housing and configured to read and writedata to one of said plurality of surficial data storage locations; asecond actuator assembly supporting said second read/write head andconfigured to move said second read/write head independently of saidfirst read/write head and so that said second read/write head is able toaccess said plurality of surficial data storage locations; and acontroller operatively connected to said first actuator assembly andsaid second actuator assembly, said controller responsive to theplurality of temporally sequential data transfer requests by performingsaid plurality of corresponding respective seeks in the temporallysequential order by alternating the plurality of correspondingrespective seeks between said first actuator assembly and secondactuator assembly, said controller operatively configured to stall onesof the plurality of corresponding respective data transfers as needed tomaintain the plurality of corresponding respective data transfers in anorder consistent with the temporally sequential order of the pluralityof data transfer requests.
 15. A disk drive system according to claim14, wherein said controller is further responsive to the plurality oftemporally sequential data transfer requests by performing saidplurality of corresponding respective seeks in the temporally sequentialorder by sequentially alternating the plurality of correspondingrespective data transfers between said first and second read/writeheads.
 16. A disk drive system according to claim 14, further comprisinga plurality of platters each including a first and second data storagesurface, said plurality of surficial data storage locations beingcontained on said first and second data storage surfaces of saidplurality of platters, the disk drive system further comprising a firstset of read/write heads supported by said first actuator assembly and asecond set of read/write heads supported by said second actuatorassembly, each of said first and second sets of read/write heads havinga read/write head operable with a corresponding respective one of saidfirst and second storage surfaces of said plurality of platters.